Process for the preparation of precipitated calcium carbonates



United States Patent I 3 003 010 I V rnocnss FOR THE fiREi ARATIoN orPRECIPI- TATED CALCIUM CARBONATES Fernand Meuret, Heusden, and VictorBrouwers, Malines,

precipitated calcium carbonate is used, prepared by carbonation of milkof lime according to the current technique, and is designated by CaCO(I); in the other a precipitated calcium carbonate is used which hasbeen I 5 prepared under exactly the same conditions as CaCO gi g ga zggfi Solvay & Brussels Belgmm (I), but in the presence of anarnount ofaluminium ions No Drawing Filed Man 17 1958, Sen 721,671 of g. perkilogram of precipitated calcium carbonate.

Claims priority, application Belgium Mar. 26, 1957 Thls 1s designated byCaCOs 5 Claims. (Cl. '260-762) Example 1 The present invention concernsa process for the The}? Was P p duplicate) a vulcanisate of thepreparation of extremely fine grained precipitated calcium fOllOWlflgformula carbonate particularly suitable as a white reinforcing filler,especially for rubber, natural or synthetic, and as a e lO Circle rubber(medlum vulcamzatlon pigment for the preparation of paper coatings. p100 It is known that the crystalline form of precipitated Z110 V 5calcium carbonate particularly suitable as a reinforcing Steam; 2 fillerfor rubber is rhombohedral calcite with dimensions Sulphur 3 less than 1micron Phenyl-B-naphthylamine -4 0.5

It is likewise known that there are difiiculties encoun-Aldol-vl-naphthylamifle tered in obtaining a precipitated calciumcarbonate satis- Dibenzoflliazyl flisulphide fying these conditions whenthe precipitate is prepared. DiPhellylglltlflidllle by carbonation ofmilk of lime. Akticit A The present invention concerns a process for theCacos Cacos 81 preparation of precipitated calcium carbonatesatisfactory The f ll i table shows the improvement in for use as awhite filler, being present in the desired cryssham-cal properties ofthe vulcanisates containing the tallineform and the dimensions of thoseparticles being precipitated calcium carbonate c co (11) preparedappreciably less than those of precipitated calcium care. cording to theinvention bonates for reinforcing actually on the market.

The applicants have found that it is extremely advan- 0 Properties oaooaoacos tageous to prepare precipitated calcium carbonate by the (I) (II)carbonation of milk of lime in the presence of ions, such as those ofaluminium, magnesium, vanadium, chromium Modulus 300%, k om. s4 67 orferrous iron Break strength, kgJcm. 279 290 Elongation at break,percent. 585 610 The process according to the invention for the prepara-Tear resistance, kg./cm 64 102 tion of precipitated calcium carbonate bycarbonation of i gzgfggfif fg g: g milk of lime is characterised in thatit IS effected in the presence of an amount of ions selected those ofaluminl 2 ium, magnesium, vanadium, chromium or ferrous iron, Exam? 8said amount being comprised between 0.2 and 3% by There was prepared (induplicate) a vulcanisate of the weight of the calcium carbonateprecipitated and added following formula at any moment of thepreparation. The desired amount G. of ions may, for example, be added tothe milk of lime Yellow Circle rubber (medium vulcanization before thecarbonation or to the suspension at the end speed) 100 of thecarbonation. ZnO 5 In the carrying out of the process according to theStearic acid 2 invention, it is suitable to add the above mentioned ionsSulphur 3 in the proportion of 0.2 to 3% by weight of the precipi-Phenyl-p-naphthylamine 0.5 tated calcium carbonate. The following tableshows by Aldol-o-naphthylamine 05 way of example, and without limitingthe scope of the in- Dibenzothiazyl disulphide 0.8 vention, thequantities of some of the ions successfully Diphenylguanidine 0.3 used.CaCO (I) or CaCO (II) 81 Salts! Metal content 1'11 The following tableshows the improvement in me- Cacoa Precipitated chanical properties ofthe vulcanisates containing the Na Al O 2.2 precipitated calciumcarbonate CaCO (II) prepared ac- 2( 4) a cording to the invention.MgSO.; 6 4- 2 Properties oooo, GaCO; Cr(NO .9I-I O 3.4 FeCl .H O 3.5

Among the above mentioned ions, those of aluminium ileii triiltifkgjtfiji 223 228 or magnesium are preferably selected because the saltsof @62 these metals are in general of a white colour and particu- ShoreHardness A2"-.- 42 5a larly suitable in the preparation of Whitefillers. 65 Abrasim (mm, 180 164 By adding to rubber a calcium carbonateprecipitated obtained according to the process of the invention, one WeC obtains vulcanisates with mechanical characteristics supe- 1. Aprocess for the preparation of precipitated calrior to those ofvulcanisates obtained by using a comcium carbonate particularly suitableas a filler for natural mercial precipitated calcium carbonate asreinforcing and synthetic rubber and as a pigment for paper coatingsfiller, as shown in the following examples.

Each vulcanisate is prepared in duplicate: In one a which comprises thesteps of preparing a milk of lime solution, adding to said milk of limesolution a soluble salt selected from the group consisting of sodiumaluminate (Na Al Q ),aluminum sulphate (Al (SO magnesium sulphate (MgSOvanadyl sulphate vosommo chromium nitrate (Cr(NO .9I-I O) and ferrouschloride (FeCl .H O), passing through said milk of lime a stream ofcarbon, dioxide to effect carbonation thereof and to form calciumcarbonate as a precipitate, whereby said calcium carbonate is inprecipitated form in said aqueous milk of lime in the presence of saidsoluble salt, and filtering said solution to separate said, calciumcarbonate therefrom, said soluble salt being added in an amount suchthat the metal component ofsaid salt represents 0.2 to, 3% by weight ofthe precipitated calcium carbonate.

2. A process for the preparation of precipitated calcium carbonateparticularly suitable as a filler for natural and syntheticrubber and asa pigment for paper coating which comprises the steps of preparing amilk of lime solution, passing through said milk of lime solution astream of carbon dioxide to effect carbonation thereof and to formcalcium carbonate as a precipitate, and adding to said solution at theend of the carbonation, a soluble salt selected from the groupconsisting of sodium aluminate (Na Al O aluminum sulphate (Al (SOmagnesium sulphate (MgSO vanadyl sulphate Y (VOSO .2H O) chromiumnitrate (Cr(NO .9H O) and ferrous chloride (FeCl .H O), said solublesalt being in an amount such that the metal component of said-saltrepresents 0.2 to 3% by weight of the precipitated calcium carbonate,whereby said calcium carbonate is in precipitated form in said aqueousmilk of lime in the presence of said metal component, and filtering saidsolution to separate said calcium carbonate therefrom.

3. A process for the preparation of precipitated calcium carbonateparticularly suitable as a filler for natural and synthetic rubber andas a pigment for paper coating which comprises the steps of preparing amilk of lime solution, passing through said milk of lime solution astream of carbon dioxide to effect carbonation thereof and to formcalcium carbonate as a precipitate, and filtering said solution toseparate said calcium carbonate therefrom, said solution having added toit at least prior to. said filtering a soluble salt selected from thegroup con- 4. sisting of sodium aluminate (Na Al O aluminum sulphate (Al(SO magnesium sulphate (MgSO vanadyl sulphate (VOSO .2H O), chromiumnitrate (Cr(NO .9H O) and ferrous chloride (FeCl .H O), said solublesalt being in an amount such that the metal component of said saltrepresents 0.2 to 3% by weight of the precipitated calcium carbonate,whereby said calcium carbonate is in precipitated form in said aqueousmilk of lime in the presence of said metal component.

4. A vulcanizate of an elastomer selected from the group consisting ofnatural rubber and synthetic rubber containing white filler consistingessentially of precipitated calcium carbonate,isaid calcium carbonatebeing produced by the steps of preparing a milk of lime solution,passing through said milk oflime solution a stream of carbon dioxide toeifect carbonation thereof and to form calcium carbonate as aprecipitate, and filtering said solution to separate said calciumcarbonate therefrom, said solution having added to it at least prior tosaid filtering a soluble salt selected from the group consisting ofsodium aluminate (Na Al O aluminum sulphate (AI (SO magnesium sulphate(MgSO vanadyl sulphate (VOSO 2H O) chromium nitrate (Cr(NO .9H O) andferrous chloride (FeCI I-I O), said soluble salt being in an amount suchthat the metal component of said salt represents 0.2 to 3% by weight ofthe precipitated calcium carbonate, whereby said calcium carbonate is inprecipitated form in said aqueous milk of lime in the presence of saidmetal component.

5. The vulcanizate, defined in claim 4, wherein said calcium carbonatehas a particle size of less than 0.1 micron.

References Cited in the file of this patent UNITED STATES PATENTS1,595,416 Rafsky Aug. 10, 1926 1,994,271 Church et a1. Mar. 12, 19352,068,039 Rafton Jan. 19, 1937 2,242,228 Bradner May 20, 1941 2,287,440McCleary June 23, 1942 2,520,850 Minnick Aug. 29, 1950 2,636,830 WallApr. 28, 1953 2,700,655 Endres Jan. 25, 1955

1. A PROCESS FOR THE PREPARATION OF PRECIPITATED CALCIUM CARBONATEPARTICULARLY SUITABLE AS A FILLER FOR NATURAL AND SYNTHETIC RUBBER ANDAS A PIGMENT FOR PAPER COATINGS WHICH COMPRISES THE STEPS OF PREPARING AMILK OF LIME SOLUTION, ADDING TO SAID MILK OF LIME SOLUTION A SOLUBLESALT SELECTED FROM THE GROUP CONSISTING OF SODIUM ALUMINATE (NA2AL2O4),ALUMINUM SULPHATE (AL2(SO4)3), MAGNESIUM SULPHATE (MGSO4), VANADYLSULPHATE